Samsung 860 QVO 1TB Solid State Drive (MZ-76Q1T0) V-NAND review
Samsung 860 QVO 1TB Solid State Drive (MZ-76Q1T0) V-NAND review
FORDecent endurance for a QLC SSDBuild quality
AES 256-bit encryption with Windows BitLocker support
AGAINST
High introductory MSRP
Write performance after SLC cache exhausts
Three-year warranty
Product 860 QVO 1TB 860 QVO 2TB 860 QVO 4TB
Capacity (User / Raw) 1000GB / 1024GB 2000GB / 2048GB 4000GB / 4096GB
Form Factor 2.5" 7mm 2.5" 7mm 2.5" 7mm
Interface / Protocol SATA 6.0 Gb/s / AHCI SATA 6.0 Gb/s / AHCI SATA 6.0 Gb/s / AHCI
Controller Samsung MJX Samsung MJX Samsung MJX
DRAM 1GB LPDDR4 2GB LPDDR4 4GB LPDDR4
NAND Flash Samsung QLC V-NAND Samsung QLC V-NAND Samsung QLC V-NAND
Sequential Read 550 MB/s 550 MB/s 550 MB/s
Sequential Write 520 MB/s 520 MB/s 520 MB/s
Random Read 96,000 97,000 97,000
Random Write 89,000 89,000 89,000
Encryption AES 256-bit, TCG/Opal V2.0, IEEE1667 AES 256-bit, TCG/Opal V2.0, IEEE1667 AES 256-bit, TCG/Opal V2.0, IEEE1667
Endurance 360 TBW 720 TBW 1,440 TBW
Part Number MZ-76Q1T0 MZ-76Q2T0 MZ-76Q4T0
Warranty 3-Years 3-Years 3-Years
The introduction of four bit per cell (QLC) NAND flash memory continues with Samsung's launch of their first consumer SATA SSD with QLC NAND. The new 860 QVO establishes a new entry-level tier in Samsung's highly successful SSD product family. Unlike previous low-end offerings like the 750 EVO and the plain 850, the 860 QVO is getting a broad release and is here to stay.
Samsung 860 QVO: Koo-vo?
The Samsung 860 QVO is the first of a new wave of SATA SSDs that should be able to beat the prices on even DRAMless TLC-based SSDs thanks to the increased density of QLC NAND—and the 860 QVO itself is equipped with a full-size LPDDR4 DRAM cache.
Samsung 860 QVO Primary Specifications
Capacity 1 TB 2 TB 4 TB
Form Factor 2.5" 7mm SATA
Controller Samsung MJX
NAND Flash Samsung 1Tb 64L 3D QLC
DRAM (LPDDR4) 1 GB 2 GB 4 GB
Sequential Read 550 MB/s
Sequential
Write SLC Cache 520 MB/s
QLC 80 MB/s 160 MB/s 160 MB/s
Warranty 3 years
Write Endurance 360 TB
0.3 DWPD 720 TB
0.3 DWPD 1440 TB
0.3 DWPD
Samsung's consumer SATA product line now consists of the 860 QVO, 860 EVO and 860 PRO. The 860 QVO, EVO and PRO all share a common hardware platform based around Samsung's MJX SSD controller and their 64-layer 3D NAND, with the product tiers differing primarily in the number of bits stored per flash memory cell.
The 860 QVO, from the box, is given a write endurace rating equivalent to 0.3 Drive Writes Per Day (DWPD), which even for the 1TB means 300GB a day, every day, which goes above and beyond most consumer workloads. Pricing is set to run at for the smallest 1TB model
making an equal cost per GB for the full range. It should be noted that the introductory MSRPs for the 860 QVO are not that aggressive in comparison to the record-setting sales we've been seeing on TLC SSDs recently.
MLC vs TLC vs QLC: Why QLC Matters
Two bit per cell MLC as used in the 860 PRO is now quite rare in the consumer SSD market and almost entirely absent from current enterprise SSD, having been largely replaced by three bit per cell TLC as used in the 860 EVO. With each increase in bits stored per cell, performance and write endurance decrease as SSDs need to be more careful to correctly discriminate between voltage levels, now up to 16 for QLC NAND.
While controller advances and other NAND process improvements (especially the switch from planar to 3D NAND) allowed TLC to overcome almost all of its disadvantages relative to MLC, QLC NAND is not expected to do the same. Early projections for QLC NAND called for at most a few hundred program/erase cycles, which would produce drives that would require careful treatment with workload that treated the storage more or less as a write-once, read-many (WORM) media. As QLC got closer to mass production, the story shifted and it became clear that QLC NAND would have adequate endurance for use as general-purpose storage.
Intel and Micron were the first to ship their QLC NAND, initially in the Micron 5210 ION enterprise SATA SSD and then in the Intel 660p and Crucial P1 consumer M.2 NVMe SSDs. The 660p and P1 introduced QLC NAND to the consumer SSD market, but as NVMe drives they still carry a price premium over SATA SSDs. However, as mentioned above, the introductory MSRPs for the 860 QVO are not at all aggressive in comparison to the record-setting sales we've been seeing on TLC SSDs recently. Those sales are not due entirely to the holiday season—flash memory prices in general have been crashing now that everyone has their 64-layer NAND in full mass production while PC and smartphone sales have been slowing. Meanwhile, rumors indicate that yields on QLC NAND have been poor, so the true cost is close to that of TLC instead of reflecting the ideal 25% discount per-GB.
Samsung 860 QVO Secondary SpecificationsCapacity1 TB2 TB4 TBDRAM (LPDDR4)1 GB2 GB4 GBSLC Cache
SizeMin6 GB6 GB6 GBMax42 GB78 GB78 GBSequential Read550 MB/sSequential
WriteSLC Cache520 MB/sQLC80 MB/s160 MB/s160 MB/sRandom
Read IOPSQD17.5k (SLC)
4.4k (QLC)QD3296k (SLC)
36k (QLC)97k (SLC)
60k (QLC)Random
Write IOPSQD142k (SLC)
21k (QLC)42k (SLC)
38k (QLC)QD3289k (SLC)
21k (QLC)89k (SLC)
40k (QLC)89k (SLC)
42k (QLC)PowerRead2.1 W2.3 W2.3 WWrite2.2 W3.1 W3.1 WIdle30 mW30 mW30 mWDevSlp3 mW3.5 mW7 mW
The two main shortcomings of QLC NAND relative to the more mainstream TLC NAND are in write performance and write endurance. Both problems can be alleviated by the use of more NAND total, allowing writes to be spread across more NAND dies in parallel. That and the (hopes of) lower prices make QLC NAND best suited for large capacity SSDs. Thus, the 860 QVO product line starts at 1TB. Even at that capacity, the 860 QVO only needs 8 dies of QLC NAND and can only sustain writes at 80 MB/s. That means that the SLC write cache on the 860 QVO is even more important than for TLC SSDs. When working within the cache, the 860 QVO can saturate the SATA link with random or sequential writes. The cache functions much the same as the SLC cache on the 860 EVO, with a capacity that varies from a minimum of 6 GB when the drive is relatively full, up to 42 GB on the 1TB model or 78 GB on the 2TB and 4TB models. The Intel and Crucial consumer QLC drives also feature variable-size SLC caches but with much higher limits on the maximum cache size and a policy of retaining data in the cache until the drive needs the extra space. By contrast, the 860 QVO seems to take a more typical approach of aggressively flushing the cache during idle time in order to prepare for future bursts of write activity.
The performance specs for the 860 QVO when operating out of the SLC cache are typical for a mainstream SATA SSD. After the cache is full, performance drops significantly, with sequential writes showing the most severe effect. Power consumption is also comparable to Samsung's other recent SATA SSDs, with the 1TB model requiring a little over 2W at peak and the larger models drawing just over 3W during writes. The 2TB and 4TB models have very nearly identical performance and power ratings, indicating that 2TB of QLC is sufficient to populate all the NAND channels of the MJX controller.
The warranty and endurance ratings for the 860 QVO are the other clear area where the use of QLC NAND has its impact. The 860 QVO's warranty period is three years, typical for low-end SSDs but shorter than the 5 years that the 860 EVO and PRO carry. Write endurance is rated for 360 full drive writes, or 0.3 DWPD for the duration of the 3-year warranty. This is comparable to some of the cheaper TLC drives currently on the market, and in terms of total bytes written the 860 QVO's rating is about 80% higher than the Intel 660p and Crucial P1, despite those NVMe QLC drives having the advantage of a five-year warranty.
The 860 QVO's case follows the same basic design as Samsung's other recent SATA SSDs, but is painted dark gray instead of Samsung's traditional black. Internally, the 1TB 860 QVO illustrates how comically oversized even the 2.5" drive form factor is compared to the requirements of modern consumer SSDs. The PCB features three main BGA packages: the DRAM, the controller, and the stack of eight 1TB QLC dies. There's an empty pad on the back that can accommodate another NAND package. Samsung commonly packages up to sixteen NAND dies together, so even the 4 TB QVO may be able to get by with this same small PCB—placing DRAM becomes the more important problem. Samsung states that their current MJX controller supports up to 8TB SSDs, but there's clearly very little demand for consumer SSDs in that capacity yet. The 2.5" form factor itself can now accommodate at least 16TB, or 32TB if two PCBs are stacked in a 15mm thick drive. These capacities may show up in enterprise products, but are probably still several generations away from hitting the consumer SSD market.
Samsung has not announced a M.2 version of the 860 QVO, but that's clearly possible if the demand is there. They can probably fit even the 4TB 860 QVO onto a single-sided 80mm M.2 card.
The launch MSRPs for the 860 QVO do not compare favorably against SATA SSDs already on the market. The 860 EVO is currently below the QVO's 15 cents per GB at 1TB and 2TB capacities, and plenty of other mainstream TLC drives are priced similarly. Samsung currently has no competition in the 4TB SATA SSD space, so their 4TB 860 EVO is substantially more expensive per GB, leaving appropriate room below for the 860 QVO. In order to be a strong competitor in the consumer market, the 860 QVO really needs to priced at no more than 13 cents per GB, and that limit is liable to come down further over the next several months as flash memory prices continue to drop and QLC yields improve.
A Note on Our Testing: The Occasional Drive Failure
Samsung provided us with samples of the 1TB and 4TB 860 QVO. Testing the 1TB model went smoothly, but the 4TB 860 QVO has run into some problems causing the drive to disappear from the system interface. These issues are most noticeable when hot-swapping the drive, which is a regular part of our SATA SSD testing routine. There have also been challenges getting the 4TB drive recognized by a motherboard during the boot process, and this causes the boot to stall indefinitely on some of our systems.
It should be noted that our testing regime is fairly streunous, and we sometimes get drive failures. It happens, and only a few of them are ever drive specific.
As a result, these problems do not appear to be specific to the 860 QVO or its use of QLC NAND and have been replicated on both the 4TB 860 EVO and 4TB 860 PRO with multiple host systems, but have not occurred with any of the smaller 860s. The 3.84 TB 860 DCT and the 4TB 850 EVO have also been trouble-free, so this isn't a problem with 4TB SSDs in general. We are still working with Samsung to determine the scope and nature of these issues with the 4TB drives, and it is not yet clear whether there is a general compatibility problem or if our testing procedure has triggered a firmware bug that put our samples permanently into an uncooperative mood.
Because of these issues, some benchmark results for the 4TB drives have been delayed. Performance and price notwithstanding, I am unable to recommend any of the 4TB 860 series SSDs until I have a better understanding of the nature of the problems.
The Competition
There are no other consumer QLC SATA SSDs on the market yet, though ADATA has announced their SU630, which will feature alarmingly low capacities. The Intel 660p and Crucial P1 are the only other consumer QLC SSDs currently available, but they are priced for the NVMe market. Most of the competition for the 860 QVO will come from SATA SSDs with TLC NAND, both entry-level models with DRAMless controllers (eg. Toshiba TR200) and more mainstream models like the 860 EVO, Crucial MX500 and WD Blue. Almost all SATA SSD product lines feature a 1TB class model, but there are still relatively few 2TB models and no 4TB competitors have been announced. This will likely change as other QLC drives come to market, and even 2TB TLC drives have been getting more common this year.
AnandTech 2018 Consumer SSD Testbed
CPU Intel Xeon E3 1240 v5
Motherboard ASRock Fatal1ty E3V5 Performance Gaming/OC
Chipset Intel C232
Memory 4x 8GB G.SKILL Ripjaws DDR4-2400 CL15
Graphics AMD Radeon HD 5450, 1920x1200@60Hz
Software Windows 10 x64, version 1709
Linux kernel version 4.14, fio version 3.6
Spectre/Meltdown microcode and OS patches current as of May 2018
Samsung 860 QVO 1TB Solid State Drive (MZ-76Q1T0) V-NAND review
Energy UseThe SYSmark energy usage scores measure total system power consumption, excluding the display. Our SYSmark test system idles at around 26 W and peaks at over 60 W measured at the wall during the benchmark run. SATA SSDs seldom exceed 5 W and idle at a fraction of a watt, and the SSDs spend most of the test idle. This means the energy usage scores will inevitably be very close. A typical notebook system will tend to be better optimized for power efficiency than this desktop system, so the SSD would account for a much larger portion of the total and the score difference between SSDs would be more noticeable.
AnandTech Storage Bench - The Destroyer
The Destroyer is an extremely long test replicating the access patterns of very IO-intensive desktop usage. Like real-world usage, the drives do get the occasional break that allows for some background garbage collection and flushing caches, but those idle times are limited to 25ms so that it doesn't take all week to run the test. These AnandTech Storage Bench (ATSB) tests do not involve running the actual applications that generated the workloads, so the scores are relatively insensitive to changes in CPU performance and RAM from our new testbed, but the jump to a newer version of Windows and the newer storage drivers can have an impact.
We quantify performance on this test by reporting the drive's average data throughput, the average latency of the I/O operations, and the total energy used by the drive over the course of the test.
The QLC drives in general stand out more when looking at latency metrics than throughput, and especially when looking at 99th percentile latencies. The 1TB 860 QVO comes in last place for both average and 99th percentile latency, and all three QLC drives have worse 99th percentile latency than the DRAMless TLC drive.
The average read and write latencies of the 860 QVO are both only slightly worse than the DRAMless TLC SSD. The NVMe QLC drives are slightly faster than the mainstream SATA drives for read latency but fall behind in average write latency.
The 860 QVO actually doesn't come in last place for 99th percentile write latency, and in fact scores far better than the DRAMless TLC drive. However, the QLC drives are all still far worse off than the mainstream TLC SATA drives.
With low performance dragging out the test to a far longer duration, it's no surprise that the QLC drives all use much more energy over the course of The Destroyer than most SATA drives. The DRAMless Toshiba TR200 is an impressive exception that manages to be very efficient despite its low overall performance.
Performance
Our first test of random read performance uses very short bursts of operations issued one at a time with no queuing. The drives are given enough idle time between bursts to yield an overall duty cycle of 20%, so thermal throttling is impossible. Each burst consists of a total of 32MB of 4kB random reads, from a 16GB span of the disk. The total data read is 1GB.
Samsung’s 860 QVO SSD is an excellent everyday performer and an outstanding bargain in its 2TB and 4TB flavors. It’s also the second quad-level cell (4-bit) SSD to pass our portals, the other being Intel’s SSD 660P.
The reason I mention this competitive drive from Intel up-front is that it’s becoming clear that 4-bit NAND, while allowing greater capacity, also extracts a performance hit that vendors must work around. How well a vendor does that affects which 4-bit drive you should buy, and whether you might be better off with an MLC or TLC drive.
Note: Samsung refers to the 860 QVO as 4-bit MLC. As the acronym MLC stands for “Multi-Level Cell,” this is technically correct. However, most refer to it as quad-level cell or QLC, which is what I assume the Q in QVO stands for.
Design and features
The 860 QVO is a 2.5-inch, 7mm thick, SATA 6Gbps SSD. It’s a lighter shade of gray than most of Samsung’s SSDs, and will be available in four capacities: 1TB, 2TB, and 4TB. That last is a boon of 4-bit NAND: greater data density than 3-bit TLC, so you can fit more data in the same number of chips.
The drive provides 1GB of DRAM cache for each 1TB of capacity. The TBW (TeraBytes Written) rating is 360TB for every 1TB of capacity. The 1TB version I tested has approximately 42GB of available secondary cache (QLC, written as SLC or MLC). The 2TB and 4TB drives each get 78GB of cache.
Performance
The plain fact of the matter is that writing more bits to a NAND cell takes more time. It’s not that SLC NAND cells are so much faster than TLC or QLC cells, it’s that writing only one bit is faster. Write only one bit to TLC or QLC, and they’re nearly as fast. Write three or four bits, and they’re not even close. Hence a certain amount of the TLC (or QLC in this case) of any SSD is treated as SLC or MLC to form a secondary cache.
Using this secondary cache—again, approximately 42GB—the 860 QVO proved a very good performer in most circumstances, as you can tell from the benchmark results below. There were no performance slowdowns until our 48GB file copy tests, in which the last 4GB or so wrote at only 70MBps. This would not occur in the 2TB or 4TB drives, with their more bountiful Level 2 cache.
The burst random read performance of the Samsung 860 QVO is clearly lower than the 3D TLC competition, while the Intel/Micron QLC NVMe drives have no trouble competing against the field of mainstream SATA TLC drives. Even in the worst case of the smallest QVO being entirely full, read speeds are still vastly better than a hard drive.
Our sustained random read performance is similar to the random read test from our 2015 test suite: queue depths from 1 to 32 are tested, and the average performance and power efficiency across QD1, QD2 and QD4 are reported as the primary scores. Each queue depth is tested for one minute or 32GB of data transferred, whichever is shorter. After each queue depth is tested, the drive is given up to one minute to cool off so that the higher queue depths are unlikely to be affected by accumulated heat build-up. The individual read operations are again 4kB, and cover a 64GB span of the drive.
On the longer random read test, the Toshiba TR200 DRAMless TLC drive is no longer able to stay ahead of the 860 QVO, and even the Intel/Micron QLC drives fall behind most mainstream SATA drives (especially when full).
The power consumption of the 860 QVO during the random read test is only slightly higher than its TLC-based relatives, but that's plenty to push its efficiency scores into last place, given the poor performance.
The queue depth scaling of the 860 QVO during random reads is fairly typical in shape, with improvements starting to taper off after QD16. However, the vertical scale is important: the QVO doesn't ever reach even half the performance of the best TLC-based SATA SSDs.
Looking at the 1TB 860 QVO's random read results compared to all the other SATA drives in the benchmark database, it is clear that the QVO isn't anywhere near the cutting edge for power efficiency or peak performance, but there are worse drives out there.
Random Write Performance
Our test of random write burst performance is structured similarly to the random read burst test, but each burst is only 4MB and the total test length is 128MB. The 4kB random write operations are distributed over a 16GB span of the drive, and the operations are issued one at a time with no queuing.
The SLC cache of the 860 QVO is very effective for the burst random write test, leaving it tied or slightly ahead of the 860 EVO.
As with the sustained random read test, our sustained 4kB random write test runs for up to one minute or 32GB per queue depth, covering a 64GB span of the drive and giving the drive up to 1 minute of idle time between queue depths to allow for write caches to be flushed and for the drive to cool down.
On the longer random write test, the larger SLC cache and greater parallelism of the 4TB 860 QVO helps it keep pace with other top SATA SSDs, but the 1TB QVO has to settle for being slightly faster than the DRAMless TLC drive.
The QVO is again a bit more power hungry than most of the TLC drives, which doesn't hurt the 4TB QVO's efficiency score much thanks to its good performance, but the 1TB QVO ends up tied for last place with the full-drive performance from the Intel/Micron QLC drives.
The 1TB 860 QVO shows very little random write performance scaling with increasing queue depth, though power consumption does go up significantly from QD1 to QD2. The 4TB 860 QVO shows a much more typical scaling up to saturation at QD4, with a performance curve that is almost an exact match for the 4TB 860 EVO.
There are some TLC SATA SSDs that draw the same power to deliver half the random write performance of the 1TB 860 QVO, but in the grand scheme of things the 1TB QVO's results on this test are sub-par. The 4TB starts out in the same spot but ends up hitting the SATA performance wall without consuming too much power.
Idle Power Measurement
SATA SSDs are tested with SATA link power management disabled to measure their active idle power draw, and with it enabled for the deeper idle power consumption score and the idle wake-up latency test. Our testbed, like any ordinary desktop system, cannot trigger the deepest DevSleep idle state.
Idle power management for NVMe SSDs is far more complicated than for SATA SSDs. NVMe SSDs can support several different idle power states, and through the Autonomous Power State Transition (APST) feature the operating system can set a drive's policy for when to drop down to a lower power state. There is typically a tradeoff in that lower-power states take longer to enter and wake up from, so the choice about what power states to use may differ for desktop and notebooks.
We report two idle power measurements. Active idle is representative of a typical desktop, where none of the advanced PCIe link or NVMe power saving features are enabled and the drive is immediately ready to process new commands. The idle power consumption metric is measured with PCIe Active State Power Management L1.2 state enabled and NVMe APST enabled if supported.
Samsung’s 860 QVO comes in a standard 2.5-inch 7mm form factor and connects to the host via a SATA 6GB/s connection. It has a sleek-looking full metal casing.
Inside the case, the 1TB model has one of the smallest PCBs we've seen, similar to the 860 EVO. The PCB hosts a single SSD controller, DRAM package, and NAND package. The 2.5” form factor seems like overkill given the size of the components, but the large case is needed to ensure compatibility with existing standards.
We see the same MJX controller as the one found in Samsung's EVO and PRO models, so compatibility and stability should not be an issue in most environments. The controller also supports LPDDR4 DRAM to improve power efficiency. Each QVO capacity point features a 1MB:1GB DRAM to flash ratio, meaning the 1TB model has a 1GB LPDDR4 DRAM package while the 4TB model has 4GB of LPDDR4. Memory products still command a premium during the ongoing shortage, so the DRAM allocation is an interesting choice considering most companies are using less DRAM to reduce costs. The Intel 660p, for example, only needs 256MB of DRAM for the 1TB model.
The flash has a die density of 1Tb, and there are a total of 8 dies stacked into a single package. The 1TB SSD provides 931.5GB of usable capacity after formatting. It is striking that Samsung can cram in 1TB of its V4 QLC flash into a single package and still deliver solid performance. Typically, SSDs need several flash packages working in concert, thus exploiting the benefits of parallelism, to reach similar levels of performance.
AS SSD 2.0 had roughly the same opinion as CrystalDiskMark about the 860 QVO’s speediness. Note that this test isn’t as optimistic about the throughput, erring slightly on the low side of what we see in our real-world, 48GB copy tests.
Seek times, as shown below, are actually quite quick compared to most SATA 6Gbps SSDs. This may have something to do with the previously described and generous allotment of DRAM cache.
Below you can see that the copy tests were only mildly affected by the 860 QVO’s running out of cache, but that was only because such a small amount of data was written to the main body of QLC memory. Double this test size, and the 1TB 860 QVO and Kingston’s bars would’ve been far longer than the Sony’s or Seagate’s. Even the 2TB and 4TB capacities would run dry in that scenario.
The area where the 860 QVO (blue bars) falls short is in writing large amounts of data, a trait it shares with the Kingston HyperX Fury (purple bars). The more data you write, the worse the times will be. The pace of the 860 QVO hovers around 70MBps once the cache is overwritten. Shorter bars are better.
When the 860 QVO runs out of cache, it’s pretty depressing. The drive will clear the cache by writing the data to the main body of 4-bit NAND, but that process takes a while. I waited a good ten minutes between tests. Below you can see what happened when I didn’t wait that long to try copying 48GB one more time. The original 48GB copy didn’t slow down until about the 90-percent mark.
Just by way of comparison, in terms of sustained throughput, we’ve seen hard drives clock 250MBps. But even when writing slowly, SSDs retain their super-fast seek times. Also note, this is strictly about writing. NAND read speeds in SATA SSDS remain quick no matter what the number of bits being read.
A good drive for the mainstream user
The 860 QVO is a great SSD most of the time, but there are a number of cheaper 1TB competitors that don’t slow down. The 2TB and 4TB drives, on the other hand, are a couple of hundred dollars less than the competition and don’t fall out of cache nearly as soon. That’s a big-enough price difference that I’d consider the trade-off, which will vary in balance depending on your needs, worthwhile.
Bargain or not, know that you will see a massive drop-off in performance when the drive runs out of cache. It doesn’t run out often, but it’s ugly when it does.
Conclusion
The Samsung 860 QVO is not the first consumer QLC SSD we've tested, but in many ways it better conforms to our expectations for QLC than the Intel 660p and Crucial P1 did. Those NVMe SSDs don't do much to satisfy demand for a cheap entry-level drive or for a high-capacity drive, the two applications where QLC NAND seems most useful. QLC has been pitched to us several times as a HDD replacement, rather than a performance product. It was a bit of a surprise to see QLC first arrive in NVMe SSDs. By contrast, the 860 QVO is an extremely predictable product with no surprises whatsoever in its design. Samsung is building on a tried and true formula, just adapting the 860 EVO to work with QLC NAND.
QLC NAND is fundamentally about sacrificing quality for quantity. The viability of QLC SSDs rests on the assumption that existing drives are more than fast enough, which is something that's certainly true of many Samsung SSDs. The Samsung 860 QVO is not as fast or as power efficient as the 860 EVO, but it doesn't need to be. Samsung has tended to stay out of the true entry-level segment of the SSD market, and there's been room for something like the QVO in their product lineup for much longer than they've had the technology to make a QLC SSD.
Note: Samsung refers to the 860 QVO as 4-bit MLC. As the acronym MLC stands for “Multi-Level Cell,” this is technically correct. However, most refer to it as quad-level cell or QLC, which is what I assume the Q in QVO stands for.
Design and features
The 860 QVO is a 2.5-inch, 7mm thick, SATA 6Gbps SSD. It’s a lighter shade of gray than most of Samsung’s SSDs, and will be available in four capacities: 1TB, 2TB, and 4TB. That last is a boon of 4-bit NAND: greater data density than 3-bit TLC, so you can fit more data in the same number of chips.
The drive provides 1GB of DRAM cache for each 1TB of capacity. The TBW (TeraBytes Written) rating is 360TB for every 1TB of capacity. The 1TB version I tested has approximately 42GB of available secondary cache (QLC, written as SLC or MLC). The 2TB and 4TB drives each get 78GB of cache.
Performance
The plain fact of the matter is that writing more bits to a NAND cell takes more time. It’s not that SLC NAND cells are so much faster than TLC or QLC cells, it’s that writing only one bit is faster. Write only one bit to TLC or QLC, and they’re nearly as fast. Write three or four bits, and they’re not even close. Hence a certain amount of the TLC (or QLC in this case) of any SSD is treated as SLC or MLC to form a secondary cache.
Using this secondary cache—again, approximately 42GB—the 860 QVO proved a very good performer in most circumstances, as you can tell from the benchmark results below. There were no performance slowdowns until our 48GB file copy tests, in which the last 4GB or so wrote at only 70MBps. This would not occur in the 2TB or 4TB drives, with their more bountiful Level 2 cache.
The burst random read performance of the Samsung 860 QVO is clearly lower than the 3D TLC competition, while the Intel/Micron QLC NVMe drives have no trouble competing against the field of mainstream SATA TLC drives. Even in the worst case of the smallest QVO being entirely full, read speeds are still vastly better than a hard drive.
Our sustained random read performance is similar to the random read test from our 2015 test suite: queue depths from 1 to 32 are tested, and the average performance and power efficiency across QD1, QD2 and QD4 are reported as the primary scores. Each queue depth is tested for one minute or 32GB of data transferred, whichever is shorter. After each queue depth is tested, the drive is given up to one minute to cool off so that the higher queue depths are unlikely to be affected by accumulated heat build-up. The individual read operations are again 4kB, and cover a 64GB span of the drive.
On the longer random read test, the Toshiba TR200 DRAMless TLC drive is no longer able to stay ahead of the 860 QVO, and even the Intel/Micron QLC drives fall behind most mainstream SATA drives (especially when full).
The power consumption of the 860 QVO during the random read test is only slightly higher than its TLC-based relatives, but that's plenty to push its efficiency scores into last place, given the poor performance.
The queue depth scaling of the 860 QVO during random reads is fairly typical in shape, with improvements starting to taper off after QD16. However, the vertical scale is important: the QVO doesn't ever reach even half the performance of the best TLC-based SATA SSDs.
Looking at the 1TB 860 QVO's random read results compared to all the other SATA drives in the benchmark database, it is clear that the QVO isn't anywhere near the cutting edge for power efficiency or peak performance, but there are worse drives out there.
Random Write Performance
Our test of random write burst performance is structured similarly to the random read burst test, but each burst is only 4MB and the total test length is 128MB. The 4kB random write operations are distributed over a 16GB span of the drive, and the operations are issued one at a time with no queuing.
The SLC cache of the 860 QVO is very effective for the burst random write test, leaving it tied or slightly ahead of the 860 EVO.
As with the sustained random read test, our sustained 4kB random write test runs for up to one minute or 32GB per queue depth, covering a 64GB span of the drive and giving the drive up to 1 minute of idle time between queue depths to allow for write caches to be flushed and for the drive to cool down.
On the longer random write test, the larger SLC cache and greater parallelism of the 4TB 860 QVO helps it keep pace with other top SATA SSDs, but the 1TB QVO has to settle for being slightly faster than the DRAMless TLC drive.
The QVO is again a bit more power hungry than most of the TLC drives, which doesn't hurt the 4TB QVO's efficiency score much thanks to its good performance, but the 1TB QVO ends up tied for last place with the full-drive performance from the Intel/Micron QLC drives.
The 1TB 860 QVO shows very little random write performance scaling with increasing queue depth, though power consumption does go up significantly from QD1 to QD2. The 4TB 860 QVO shows a much more typical scaling up to saturation at QD4, with a performance curve that is almost an exact match for the 4TB 860 EVO.
There are some TLC SATA SSDs that draw the same power to deliver half the random write performance of the 1TB 860 QVO, but in the grand scheme of things the 1TB QVO's results on this test are sub-par. The 4TB starts out in the same spot but ends up hitting the SATA performance wall without consuming too much power.
Idle Power Measurement
SATA SSDs are tested with SATA link power management disabled to measure their active idle power draw, and with it enabled for the deeper idle power consumption score and the idle wake-up latency test. Our testbed, like any ordinary desktop system, cannot trigger the deepest DevSleep idle state.
Idle power management for NVMe SSDs is far more complicated than for SATA SSDs. NVMe SSDs can support several different idle power states, and through the Autonomous Power State Transition (APST) feature the operating system can set a drive's policy for when to drop down to a lower power state. There is typically a tradeoff in that lower-power states take longer to enter and wake up from, so the choice about what power states to use may differ for desktop and notebooks.
We report two idle power measurements. Active idle is representative of a typical desktop, where none of the advanced PCIe link or NVMe power saving features are enabled and the drive is immediately ready to process new commands. The idle power consumption metric is measured with PCIe Active State Power Management L1.2 state enabled and NVMe APST enabled if supported.
Samsung’s 860 QVO comes in a standard 2.5-inch 7mm form factor and connects to the host via a SATA 6GB/s connection. It has a sleek-looking full metal casing.
Inside the case, the 1TB model has one of the smallest PCBs we've seen, similar to the 860 EVO. The PCB hosts a single SSD controller, DRAM package, and NAND package. The 2.5” form factor seems like overkill given the size of the components, but the large case is needed to ensure compatibility with existing standards.
We see the same MJX controller as the one found in Samsung's EVO and PRO models, so compatibility and stability should not be an issue in most environments. The controller also supports LPDDR4 DRAM to improve power efficiency. Each QVO capacity point features a 1MB:1GB DRAM to flash ratio, meaning the 1TB model has a 1GB LPDDR4 DRAM package while the 4TB model has 4GB of LPDDR4. Memory products still command a premium during the ongoing shortage, so the DRAM allocation is an interesting choice considering most companies are using less DRAM to reduce costs. The Intel 660p, for example, only needs 256MB of DRAM for the 1TB model.
The flash has a die density of 1Tb, and there are a total of 8 dies stacked into a single package. The 1TB SSD provides 931.5GB of usable capacity after formatting. It is striking that Samsung can cram in 1TB of its V4 QLC flash into a single package and still deliver solid performance. Typically, SSDs need several flash packages working in concert, thus exploiting the benefits of parallelism, to reach similar levels of performance.
AS SSD 2.0 had roughly the same opinion as CrystalDiskMark about the 860 QVO’s speediness. Note that this test isn’t as optimistic about the throughput, erring slightly on the low side of what we see in our real-world, 48GB copy tests.
Seek times, as shown below, are actually quite quick compared to most SATA 6Gbps SSDs. This may have something to do with the previously described and generous allotment of DRAM cache.
Below you can see that the copy tests were only mildly affected by the 860 QVO’s running out of cache, but that was only because such a small amount of data was written to the main body of QLC memory. Double this test size, and the 1TB 860 QVO and Kingston’s bars would’ve been far longer than the Sony’s or Seagate’s. Even the 2TB and 4TB capacities would run dry in that scenario.
The area where the 860 QVO (blue bars) falls short is in writing large amounts of data, a trait it shares with the Kingston HyperX Fury (purple bars). The more data you write, the worse the times will be. The pace of the 860 QVO hovers around 70MBps once the cache is overwritten. Shorter bars are better.
When the 860 QVO runs out of cache, it’s pretty depressing. The drive will clear the cache by writing the data to the main body of 4-bit NAND, but that process takes a while. I waited a good ten minutes between tests. Below you can see what happened when I didn’t wait that long to try copying 48GB one more time. The original 48GB copy didn’t slow down until about the 90-percent mark.
Just by way of comparison, in terms of sustained throughput, we’ve seen hard drives clock 250MBps. But even when writing slowly, SSDs retain their super-fast seek times. Also note, this is strictly about writing. NAND read speeds in SATA SSDS remain quick no matter what the number of bits being read.
A good drive for the mainstream user
The 860 QVO is a great SSD most of the time, but there are a number of cheaper 1TB competitors that don’t slow down. The 2TB and 4TB drives, on the other hand, are a couple of hundred dollars less than the competition and don’t fall out of cache nearly as soon. That’s a big-enough price difference that I’d consider the trade-off, which will vary in balance depending on your needs, worthwhile.
Bargain or not, know that you will see a massive drop-off in performance when the drive runs out of cache. It doesn’t run out often, but it’s ugly when it does.
Conclusion
The Samsung 860 QVO is not the first consumer QLC SSD we've tested, but in many ways it better conforms to our expectations for QLC than the Intel 660p and Crucial P1 did. Those NVMe SSDs don't do much to satisfy demand for a cheap entry-level drive or for a high-capacity drive, the two applications where QLC NAND seems most useful. QLC has been pitched to us several times as a HDD replacement, rather than a performance product. It was a bit of a surprise to see QLC first arrive in NVMe SSDs. By contrast, the 860 QVO is an extremely predictable product with no surprises whatsoever in its design. Samsung is building on a tried and true formula, just adapting the 860 EVO to work with QLC NAND.
QLC NAND is fundamentally about sacrificing quality for quantity. The viability of QLC SSDs rests on the assumption that existing drives are more than fast enough, which is something that's certainly true of many Samsung SSDs. The Samsung 860 QVO is not as fast or as power efficient as the 860 EVO, but it doesn't need to be. Samsung has tended to stay out of the true entry-level segment of the SSD market, and there's been room for something like the QVO in their product lineup for much longer than they've had the technology to make a QLC SSD.
Samsung 860 QVO 1TB Solid State Drive (MZ-76Q1T0) V-NAND review
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